Crane.



P. R. DAVISON.

CRANE.

APPLICATION FILED JULY 13,1911.

Patented Apr. 16,1912.

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P. R. DAVISON.

CRANE.

APPLICATION IILEI) JULY 13,1911

1,023,507. 7 Patented Apr. 16, 1912 4 SHEETS-*SHBET 2.

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1,023,507, Patented Apr. 16, 1912.

COLUMBIA PLANOORAPH co" WASHINGTON, D. C.

PL R. DAVISON.

CRANE.

\ APPLIUA'IZ'ION FILED JULY 13,1911. 7 1,023,507. Patented Apr. 16, 1912.

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PERCY RUGBY DAVISON, OF GRAVESEND, ENGLAND.

CRANE.

To all whom it may concern Be it known that I, PERoY RUGBY DAVI- SON, a subject of the King of Great Britain, residing at 42 Cobham street, Gravesend, Kent, England, have invented new and useful Improvements in and Relating to Cranes, of which the following is a specification.

This invention relates to jib cranes, derricks, and the like, actuated by electric, hydraulic or other power, and has for its object to provide means for lufling the jib in such a manner that the load is maintained at one level notwithstanding the varying angle of the said jib. Provision is also made for maintaining the balance of the jib during lufling, and balancing the load at any radius or angle.

According to the invention the lifting chain or rope is passed around multiple pulleys, one series being movable with respect to the other series, and connected to a point at the base of the jib so that as the latter is lufied to swing the load in or out the movable multiple pulleys will be moved toward or away from the fixed pulleys respectively to correspondingly pay out or take in the lifting chain or rope to maintain the level of the load.

In a suitable arrangement for carrying out the invention, the multiple pulleys are arranged in a plane passing through the pivot of the crane jib, the movable pulleys being movable in the said plane and connected by a rod or rods, to a point on the latter near the pivot thereof. The crane chain passes over a pulley at the end of the jib, then around a pulley concentric with the jib pivot and finally around the two series of pulleys to the winding gear, the ratio of purchase being proportional to the jib dimensions and the position of the point of connection of the connecting rod or rods. Or, the said pulleys may be the usual multiple pulleys of a hydraulic j igger. The balance of the jib is maintained by a weight at the base of the jib and the jib may be luffed by a chain or the like connected to a point on the base of the jib remote from the pivot of the latter or by the rod or rods connecting the movable multiple pulleys to the said base, the said pulleys in this latter case being moved for instance, by a lufiing screw in the known manner.

It will be understood that the dimensions of the jib and the mechanical advantage of the pulleys used must be so proportioned Specification of Letters Patent.

Application filed July 13, 1911.

Patented Apr. 16, 1912.

Serial No. 638,353.

that the amount of chain paid out or hauled in by any specified movement of the movable pulleys must be equal to the amount of vertical movement imparted to the upper end of the jib by the said movable pulleys.

To enable the invention to be fully understood I will describe it by reference to the accompanying drawings, in which Figure 1 is a sectional side elevation of a portion of a jib crane illustrating my improvements. Fig. 2 is a similar view illustrating a modification, and Figs. 3 and 4 are side elevations illustrating still further modifications of the invention.

Referring first to the construction illus trated in Fig. 1, a is the jib of the crane which is pivoted at b to the crane structure 0, the said jib being provided beyond the fulcrum Z) with the extension cl which carries the weight 6 at its lower extremity. f is the fixed series of multiple pulleys, these being mounted in the bearing f on the crane structure c and g is the movable series of multiple pulleys, the said pulleys being mounted in connection with a traveling nut 72, which engages with the screw rod 2'. The upper end of the screw rod 2' is in gear with, and adapted to be driven by, a motor such as an electromotor j, while its lower end is held in a bearing 70 fixed to the crane structure 0. Z is the lifting chain or rope, the said chain passing over a pulley m upon the outer end of the jib a, thence around a pulley a concentric with the fulcrum b of the jib, and thence around the multiple pulleys f and g alternately and being finally connected to the winding drum 0. The nut h is jointed to the lower extremity of the jib a by means of the rod or link 79, the length of the said rod being equal or approximately equal to the extension (Z of the jib. With this construction and with the parts properly proportioned as above set forth, it will be obvious that when the motor j is operated, the screw rod 71 is turned, so as to cause the nut hto travel along the said rod, the travel of the rod causing the jib a to rise or fall through the medium of the rod 9, and at the same time paying out or drawing in the lifting chain Z to an extent such that the load supported by the said chain remains at the same level, notwithstanding the varying angle made by the jib a with the horizontal.

Fig. 2 illustrates an arrangement in which the lifting chain Z is double and passes around a pulley block Z by which the hook angle thereto.

-head'carrying the pulleys g and actuating the link 79.

Fig. 3 shows a construction of crane which is similar to that illustrated in Fig. 1, the difference being that the two sets of -multiple pulleys f and 9 while still being in a plane containing the fulcrum Z) of the jib, are horizontal instead of vertical. The extension 61 of the jib is consequently not in alinement with the said jib, but is at an In other respects the construction is the same as that illustrated in Fig. 1, and the crane functions in the same way.

The construction illustrated in Fig. 4 is again also similar to the arrangements illustrated in Figs. 1 and 3, the difference lying in the relative arrangements of the movable and fixed pulleys and the jib. In this case the said pulleys together with the "mechanism for actuating the same, all of which are similar to those illustrated in Figs. 1 and 3, are arranged vertically, but above the fulcrum b of the jib a, the nut h in connection with the movable pulleys g being connected to the jib a by the rod 39 at a point 9 intermediate of the fulcrum b and the extremity of the jib. The operation of this form of the crane is similar to the foregoing.

It will be understood that although I have shown the improved lutfing gear as arranged horizontally and vertically it may be arranged in other positions. It is also to be understood that any other form of motor than those shown may be used in conjunction with the various modifications of the invention.

Claims:

1. In a crane, the combination with a support, of a jib pivoted thereto, a series of fixed pulleys and a series of movable pulleys, the two sets of pulleys and the point at which the jib is pivoted to said support, being in the same plane, a rod connecting the movable pulleys to the jib, and means for moving the movable pulleys relatively to the fixed pulleys.

2. In a crane, the combination with a support, of a jib pivoted thereto, a series of fixed pulleys and a series of movable pulleys, the two sets of pulleys and the point at which the jib is pivoted to the support, being in the same plane, a rod connecting the movable pulleys to the jib, and a screw provided with a nut to which said movable pulleys are adapted to be fixed whereby by the rotation of said screw the said movable pulleys are caused to move relatively to the fixed pulleys.

PERCY RUGBY DAVISON.

Witnesses C. G. REDFERN, A. ALBUTT.

fiopies of this patent may be obtained for five cents each, by addressing the "Commissioner of Patents. Washington, D. C. 

